My co-tenant has a friend that has recently become a major disturbance for me. I've lived in the house with the co-tenant for over a year without problems. His friend has been a frequent visitor since I moved in (occasionally stays overnight but visits nearly daily for several hours) Within the last 2-3 months however I started to actually build more than just a superficial "friend of a friend" relationship with him and unintentionally discovered that he's some sort of covert narcissist. Basically he does some pretty morbid things in his personal life and even at our house and will pathologically lie about all of it. Eg. - for several months he was breaking into our house while we weren't home so that he had somewhere to smoke. I actually did notice a small amount of money go missing from my room (over several months about $40) - after I discovered he was breaking in through the window and confronted him and the co-tenant (separately). My co-tenant says he knew about it and his "friend" just tried to lie about it (I had more than sufficient evidence to run him on a merry-go-round of minimal admissions to breaking in through our window because I kept revealing how I knew he was lying, although he put the foot down at having cut his own key to our property -> next point - my co-tenant's brother shares with us (no problem with this) but he gave his key to the "friend" under the pretext that the "friend" left something in the house and would immediately return it. Since this coincided with me taking measures to secure the windows I'm pretty sure he just lied to the gullible brother so he could cut the key. He had since been caught in the house while no one was home, all doors locked and all windows secured from outside entry. - he is just generally a nuisance (uses our utilities way too much without ever paying for them or even being given permission - I also banned him from the internet but I'm pretty sure the co-tenant or his brother are secretly sharing it with him. He has also been caught hacking our network with his own packet sniffer and was probably doing this for months while he had trusted access. I also suspect he's hacked one of my email accounts but that's something I can't prove, too (an email I read was tagged unread and the connection is unsecured -- since he was packet-sniffing he could easily have obtained the password). As much as I can't really prove most of this, I think this is cause for any reasonable person to consider their rights/ privacy /etc. sufficiently violated but I'm not sure what my rights are as far as a co-tenant to tell another co-tenant I flat-out don't want his friend anywhere near the house any more. Or does any co-tenant basically have the right to refuse bad guests invited by co-tenants? I'm basically at the point where I've realised I shouldn't need to be worrying about these things and / or taking such restrictive measures to secure my personal property in a shared house. Its obviously prudent to take care of security but against people that don't even live on the property? Surely I can tell him with authority under Property Law to leave and not return?